black screen

[Errol Sapir]

I restarted my computer and now have a black screen. No icons or any gui 
signs. I am in Kubuntu as everything works i.e. I am not in a command 
line mode. If I press alt/F2 I can open any program by typing its name. 
Once I am in a program it works perfectly. I can browse, read my email 
and open links and attachments. Everything is working. How do I get my 
graphic desktop back? I tried the repair mode which didn't help.
Errol